1. Field of the Invention
This invention relates to a transfer of rigid sheets from a first conveyor for moving said sheets in end to end relation along a first path while the sheets are gripped by tongs suspended from carriages to a second conveyor for moving said rigid sheets in a broadside direction along a second path parallel to the first path wherein the sheets are supported in an upright position along their lower edge. The present invention has special utility in glass sheet handling apparatus, preferably apparatus for handling glass sheets for further cooling after previous thermal treatment.
Usually, glass sheets are gripped by tongs for movement in end to end relation along a conveyor extending through a tunnel-like furnace where the glass sheets are heated to a temperature sufficient for shaping and/or tempering. When the leading glass sheet of a series of glass sheets reaches the exit of the furnace, it is within an elevated temperature range sufficient for it to be shaped to a shape desired for a curved window for an automobile side light or rear backlight or any other shape that might be desired for a glass sheet. The glass sheet so heated is shaped by press bending into the desired configuration and then the glass sheet is moved through a first cooling area along an extension of the conveyor where cold tempering medium, such as high velocity are blasts, is directed against the opposite major surfaces of the glass sheet. The glass sheet is then disengaged from the tongs and further cooled in an additional cooling area while being removed from the first cooling area. At the end of the additional cooling area, the glass sheet is inspected and packed for shipment.
If the glass sheets are moved from the first cooling area to the additional cooling area while oriented in the same end to end relation that they have during their movement through the tunnel-like furnace, the plant would have to be excessively long. However, an alternate handling system has been used to transfer the glass sheets from a first conveyor wherein tongs suspended from carriages grip the upper edge portion of the glass sheet for movement in an end to end relation through the first cooling area where the glass sheets are tempered or partially tempered. The disengaged glass sheets are dropped on to a so-called peg conveyor and more broadside for further cooling in a direction transverse to the length of the first conveyor.
This alternate conveyor system involving moving the glass sheets in a first path in end to end relation along a first conveyor and then in a second path normal to the first path along a peg conveyor while the sheets are moved in a broadside direction requires less length for a glass fabrication facility. However, where more than one production line of this type is contemplated, it is impossible to utilize factory space very efficiently, because each furnace and first cooling area would have to be staggered longitudinally of each adjacent furnace and its first cooling area in order to provide clearance for the transversely extending peg conveyors of adjacent lines. Under such circumstances, the first cooling area of one line would have to be located transversely of the hot end of the furnace of an adjacent line in order to economize plant space. Under such circumstances the need for hot temperature controls in a furnace for one production line and cold temperature controls in an adjacent cooling area for an adjacent production line makes it difficult to obtain suitable and efficient temperature control of the first cooling area of the line that is adjacent the hot end of the furnace of the one line consistent with efficient hot temperature control in the furnace.
It would be beneficial for the glass sheet tempering art to develop a conveyor system that would enable heating furnaces to be disposed side by side one another and yet not require the length of the factory to be as long as was required in the prior art. It would also be beneficial for the glass sheet treatment art to develop an alternate technique for handling glass sheets that did not require the glass sheets to be conveyed at right angles to the path taken by the glass sheet through the furnace and first cooling area of tempering apparatus.
The principles enunciated for handling glass sheets would also be suitable for handling any rigid sheet material. Therefore, the principles of this invention are equally suitable for materials other than glass sheets.
2. Description of Patents of Interests
U.S. Pat. No. 3,178,045 to Charles R. Davidson Jr. and William P. Mitchell discloses sheet handling apparatus in which a series of glass sheets are conveyed through a hot atmosphere for heating to a temperature sufficient for tempering and then through a cooling area where cold tempering medium is applied toward the glass sheets to impart at least a partial temper thereto. A peg conveyor shown in FIGS. 12 and 13 extends transversely from an unloading station through an additional cooling area. Means is provided to release the glass sheet from tongs so that the sheets are supported on their lower edge for transverse conveyance in a broadside direction along a second path transverse to the first path.
U.S. Pat. Nos. 3,530,970 and 3,610,393 to Ronald E. Richardson, Gordon F. Pereman, John D. Kellar, and Jan G. Borremans disclose and claim apparatus and method, respectively, of an alternate way to transfer glass sheets conveyed along a first path for tempering while gripped by tongs for release from the tongs and transfer to a peg conveyor to move along a second path extending transverse to the first path where the glass sheets released from tongs are supported on their bottom edges for broadside movement in a direction transverse to the first path.
Since the second path provided by the peg conveyor in each of the aforesaid patents extends in a direction transverse to the direction of the first path for conveying sheets for heat treatment operations such as involved in tempering or heat strengthening, a factory for fabricating tempered or heat strengthened glass sheets would have to have adjacent lines of production offset from one another both at their loading end at the beginning of the first path and at their unloading end. This would require an awkward arrangement of inventory of glass sheets to be handled prior to the fabrication operation. While it may be suitable for a production plant having one production line, a better arrangement would be needed if production requirements become so great as to require a second production line.
Other art called to the attention of applicant's attorney include Canadian Pat. No. 427,635 to William L. MacDemara which covers a device for transferring glass containers and Canadian Pat. No. 964,683 to Emoul J. Andersson et al. which discloses robot devices capable of providing various combinations of movement. It is considered that the robot devices of this patent would not necessarily perform the handling of rigid sheets to be described subsequently.